An LDPC code has not been used due to limitations in hardware technical capabilities in spite of excellent performance closed to the Shannon limit, but recently active researches are being conducted on the LDPC code as a channel coding technique for reducing an error rate resulting from high speed communication in next generation wired/wireless communication systems.
Such an LDPC code is on the presumption that encoding is performed in a systematic manner. In other words, a part of a packet is outputted in the same format as input bits, and the other part of the packet is outputted as additional information called parity bits (code check bits) along with the original information.
As mentioned above, every input signal has to be inputted to an LDPC code encoder so as to perform an encoding operation thereof. The ratio of parity bits in the entire packet is varied depending on a code rate. Such a code rate is fixed by an H matrix.
Meanwhile, as a prior art LDPC code encoding technique, there is an article, entitled “Efficient Encoding of Low Density Parity Check Codes” proposed by Richardson (see IEEE Transactions On Information Theory Vol. 47, NO. 2, Feb. 2, 2001).
In such a prior art technique, the H matrix is first divided into sub-matrices. Then, when an input vector of a simultaneous equation of the matrix is given, output parity bits thereof are generated.
Recently, an LDPC code encoding technique, which is simpler than the LDPC code encoding technique by Richardson set forth above, has been proposed in IEEE 802.16e by Motorola Inc. This LDPC code encoding technique encodes an LDPC code by obtaining parity bits directly through a simultaneous equation, rather than by matrix operation.
However, the LDPC code encoding technique by Richardson has the problem that it is not easy to process signals at a high speed due to the operation for dividing into sub-matrices, and the LDPC code encoding technique by Motorola Inc. has the problem that encoding complexity and hardware resource load increase considerably because it directly derives parity bits.
Consequently, in the encoding of an LDPC code, there is an urgent need for a technique which is suitable for high speed communication and can minimize encoding complexity and resource consumption.